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The effect of ultrasonic nanocrystalline surface modification (UNSM) on the water droplet erosion (WDE) performance of Ti 6Al 4V was studied. It was observed that UNSM induces deep levels of compressive residual stresses in both the scanning and transverse directions. The treated surface revealed microdimples in a micro-tracked fashion. Mechanical deformation marks were observed within the grains due to excessive plastic deformation and variation in grain size was observed across the ultrasonically modified layer. Microhardness of the UNSM condition was enhanced significantly as compared with the untreated (As-M) condition. The WDE performance tests for the UNSM and As-M conditions were conducted in a rotating disc rig in accordance with ASTM G73 standard. Influence of impact speed on WDE was explored on two different sample geometries (T-shaped flat and airfoil). WDE results showed that the flat UNSM samples had enhanced WDE performance at speeds 250, 275 and 300 m/s as compared with the As-M condition. At 350 m/s, both UNSM and As-M conditions showed similar performance. UNSM airfoil samples showed mild enhancement in the WDE performance at 300 m/s during the advanced stage as compared with the As-M condition. At 350 m/s, the UNSM airfoils do not show enhancement in WDE performance. [ABSTRACT FROM AUTHOR]

This study explored the corrosion resistance of 7075-T6 aluminum alloy by immersing it in a 3.5% NaCl solution to induce corrosion damage, and subsequently repairing the sample surface using ultrasonic nanocrystal surface modification (UNSM). UNSM was found to effectively repair the defects on the surface of the pre-corroded sample and improve its stress corrosion crack (SCC) resistance. The improvement in corrosion resistance and SCC resistance of sample was mainly due to the compressive residual stress and grain refinement caused by UNSM, which not only improved the pitting resistance but also effectively inhibited the initiation and extension of stress corrosion cracks. • UNSM refined the grains and increased the hardness of the surface layer. • UNSM introduced compressive residual stresses in the surface layer. • UNSM improved the corrosion resistance and SCC resistance of aluminum alloy. • UNSM can effectively repair corrosion damage of aluminum alloy. [ABSTRACT FROM AUTHOR]